Document Type

Lecture

Publication Date

3-3-2016

Abstract

Changes in primary ocean productivity play a key role in determining the structure and biomass yield of the North Pacific ecosystem. Archaeofaunal remains of marine mammals from the Aleutian Islands, Alaska were used as a proxy for marine productivity changes over decade, century and millennial scales throughout the Holocene. Marine vertebrate remains from several previously excavated, welldated archaeological deposits on Unalaska Island span the period AD 1912-5500 BP. Stable carbon and nitrogen isotope ratios (δ 13C and δ 15N) derived from marine mammal bone and tooth collagen provide information about changes in food web dynamics and marine productivity levels and, through inference, about ecosystem changes. The paleorecord of phytoplankton production, in response to changes in atmospheric and oceanic fluctuations, is reflected in the stable isotope composition of the skeletal remains of these animals. An analysis of over five hundred pinniped, fissiped, and cetacean individuals over the six thousand year period indicated a consistent inverse relationship existed between the two isotopes. When the δ 13C, an indication of primary production, increased, δ 15N, trophic position, decreased. The implication is as production increases in a region, the need to forage through multiple trophic levels for enough food to sustain oneself is diminished, and survivability based on resources is increased. A minimum of five time periods occurred when both stable isotopes changed from either a positive to negative slope or negative to positive slope. Historical fluctuations and their resultant impact on marine mammals and their ecosystems can give context to environmental changes on modern marine mammals.